Device and system for pressure sensing and control

ABSTRACT

Embodiments of the present invention provide devices and systems in which pressure sensing and pressure control capabilities are integrated. One embodiment of the present invention can include a device for pressure sensing and control comprising a sensor portion operable to sense a pressure and a control portion. The control portion can be operable to compare the sensed pressure to a set point; generate a control signal based on a difference between the sensed pressure and the set point; and output the control signal. The sensor portion and the control sensor portion and control portion can be integrated in a housing.

TECHNICAL FIELD OF THE INVENTION

This invention relates generally to systems for pressure monitoring andcontrol. More particularly, the present invention relates to a gaugewith integrated pressure control capability.

BACKGROUND OF THE INVENTION

Many of the processes used to manufacture computer chips or integratedcircuits take place at a controlled pressure that is less thanatmospheric pressure. If the pressure changes, even by a small amount,the properties of the circuits being worked upon can change. This canproduce an unusable batch of circuits. Therefore, to ensure batchquality, pressure levels in the process chamber must be controlled witha reasonable degree of accuracy. Typically, the pressure is continuouslycontrolled through a feedback control loop process. One of the mostcommon systems to control pressure utilized by the semiconductormanufacturing industry is illustrated in FIG. 1.

FIG. 1 is a diagrammatic representation of a portion of typical priorart semiconductor manufacturing system 20. System 20 includes a processchamber 22 in which semiconductor components are fabricated, a gauge 24to measure the pressure in process chamber 22, and a vacuum pressurecontroller 26 to compare the measured pressure from gauge 24 with asystem set point. System 20 can also include a throttle valve 28 (e.g.,a throttling gate valve, a poppet valve, a butterfly valve or othervalve known in the art) attached to a vacuum pump (not shown) toregulate a flow of gas out of process chamber 22. Valve 28 can bethrottled by valve drive 30 in response to control signals from vacuumpressure controller 26.

In operation, process chamber 22 can receive a flow of gas necessary forthe manufacturing process (e.g., gas flow 32). The gas constituting gasflow 32 can depend on the particular manufacturing process being carriedout in process chamber 22. As already noted, in order to ensure thequality of semiconductors and semiconductor components produced inprocess chamber 22 the gas pressure within process chamber 22 must beaccurately controlled. This can be achieved by throttling valve 28 toregulate the flow of gas out of process chamber 22. To appropriatelythrottle valve 28, gauge 24 can read the pressure in process chamber 22and send a signal (e.g., pressure signal 34) representing the pressurein process chamber 22 to a separate vacuum pressure controller 26.Pressure controller 26 can compare pressure signal 34 to a system setpoint (e.g., represented by set point signal 36) based on internalhardware and/or software algorithms which are well-known in the art. Setpoint signal 36 is typically provided by a control computer (not shown)which governs the entire manufacturing process. If pressure signal 34varies from set point signal 36 according to pressure vacuum controller26's internal algorithms, pressure vacuum controller 26 can generatecontrol signal 38. Valve drive 30 can receive control signal 38 andthrottle valve 28 appropriately. By adjusting valve 28, the net speed ofan output flow 39 from process chamber 22 can be changed, therebyregulating the pressure in process chamber 22. Pressure is typically notregulated, however, by changing the pumping characteristics ofdownstream vacuum pumps.

System 20 of FIG. 1 typically has several shortcomings. Because pressurevacuum controller 26, gauge 24 and valve drive 30 are separate units, asignificant number of cables are required. Due to the increased numberof cables there is a greater chance a signal will encounter interferencefrom the power cable or power source. Additionally, the large number ofcables required for system 20 can be exceedingly expensive and canrequire a significant amount of setup time.

To overcome several of these deficiencies additional systems have beendeveloped. FIG. 2 illustrates a semiconductor manufacturing system 40 inwhich pressure vacuum controller 26 and valve drive 28 are combined.System 40 includes a process chamber 22 in which semiconductorcomponents are fabricated the gauge 24 to measure the pressure inprocess chamber 22 and a combined pressure vacuum controller 26 andvalve drive 30 (e.g., unit 42). Unit 42 can govern valve 28 to regulatethe pressure in process chamber 22. Again, gauge 24 can read thepressure in process chamber 22 and send a signal (e.g., pressure signal34) representing the pressure in process chamber 22 the unit 42. Thepressure vacuum controller 26 and unit 42 can compare pressure signal 34with them with a set point signal 36. Based on the comparison of setpoint signal 36 to pressure signal 34, pressure vacuum controller 26 cangenerate control signal 38 to control valve drive 30. Valve drive 30 canthrottle valve 28 according to the control signal, thereby regulatingthe pressure in process chamber 22. Because pressure vacuum controller26 and valve drive 30 are combined in unit 42, the number of cablesrequired relative to system 20 is reduced, thereby decreasing costs andthe probability that interference in a signal cable can occur.Additionally, by combining devices, physical space is saved, thoughvalve drive 30 with vacuum pressure control 26 (e.g., unit 42) is largerthan valve drive 30 alone.

However, system 40 also suffers from several deficiencies. A majordeficiency for system 40 is that valve 28 can vibrate, sometimessignificantly, causing noise in signals produced by vacuum pressurecontroller 26. The vibrations can emanate from several sources includingthe downstream vacuum pumps or valve drive 30. The signal noise createdby the vibrations can lead to a reduction in accuracy. Additionally,because valve drive 30 generally utilizes a high-voltage DC motor tothrottle valve 28, pressure vacuum controller 26 can experiencesignificant interference that can reduce the accuracy of overallpressure control. Thus, although interference due to extensive cablingis reduced, overall interference can increase.

A further disadvantage of system 40 is that valve 28 and valve drive 30are usually difficult to maintain and replace. Because pressure vacuumcontroller 26 is combined with valve drive 30, pressure vacuumcontroller 26 is, consequently, also difficult to maintain or replace.If there is a fault in pressure vacuum controller 26, system 40 may haveto be shut down for a significant period of time, leading to potentiallymillions of dollars in lost profit.

SUMMARY OF THE INVENTION

Embodiments of the present invention provide devices that reduce oreliminate the disadvantages associated with prior art pressure controldevices and systems. More particularly, embodiments of the presentinvention provide devices and systems in which pressure sensing andpressure control capabilities are integrated.

One embodiment of the present invention can include a device forpressure sensing and control comprising a sensor portion and a controlportion. The sensor portion can be operable to sense a pressure and thecontrol portion can be operable to compare the sensed pressure to a setpoint, generate a control signal based on a difference between thesensed pressure and the set point, and output the control signal. Thesensor portion and the control sensor portion and control portion can beintegrated in a housing.

Another embodiment of the present invention can include a system forpressure control comprising a process chamber, a valve in fluidcommunication with the process chamber, a valve drive responsive to acontrol signal to open and close the valve and a gauge with integratedpressure control coupled to the process chamber. The gauge withintegrated pressure control can comprise a sensor portion at leastpartially exposed to a fluid in the process chamber operable to sense apressure in the process chamber and a control portion operable tocompare a sensed pressure to a set point, generate the control signalbased on a difference between the sensed pressure and the set point, andoutput the control signal. The control portion and sensor portion can beintegrated in a housing.

Yet another embodiment of the present invention can include a gauge withintegrated pressure control. The gauge can comprise a pressure sensor tooutput a sensed pressure, a processor coupled to the pressure sensor,and a memory accessible by the processor storing software executable bythe processor. The software instructions can comprise instructionsexecutable to receive the sensed pressure, compare the sensed pressureto a set point, and generate a control signal based on a differencebetween the sensed pressure and the set point.

The present invention provides technical advantages over prior artprocess control systems by reducing signal interference. Because thepressure controller is integrated with a gauge, there are fewer cablesin which interference can occur. Additionally, because the pressurecontroller is not located at a valve drive, the pressure controller willreceive less or no interference from the valve drive motor.

The present invention provides another technical advantage by reducingprocess chamber downtime. Downtime can be decreased because the gaugewith the integrated pressure control capability can easily be switchedout or replaced.

The present invention provides yet another important technical advantageby reducing cabling. By reducing cabling, the costs associated withcabling are also reduced.

The present invention provides yet another important technical advantageby saving space.

The present invention provides yet another important technical advantageby reducing the effects of system vibration on the pressure controller,thereby increasing reliability.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention and theadvantages thereof may be acquired by referring to the followingdescription, taken in conjunction with the accompanying drawings inwhich like reference numbers indicate like features and wherein:

FIG. 1 illustrates a prior art system for process control insemiconductor manufacturing;

FIG. 2 illustrates another prior art system for process control insemiconductor manufacturing;

FIG. 3 is a diagrammatic representation of a system for pressure sensingand control implementing a gauge with integrated pressure controlcapability according to the teachings of the present invention;

FIG. 4 is a diagrammatic representation of one embodiment of a pressuregauge with integrated pressure control capability according to thepresent invention; and

FIG. 5 is a flow chart illustrating one embodiment of a method forgenerating a control signal.

DETAILED DESCRIPTION OF THE INVENTION

Preferred embodiments of the present invention are illustrated in theFIGUREs, like numerals being used to refer to like and correspondingparts of the various drawings.

Pressure controllers are commonly used in semiconductor manufacturing aspart of a control process to govern gas pressure within a processchamber. A pressure gauge can read the gas pressure within the processchamber and a pressure controller can compare the detected or measuredpressure with a set point. A difference between the detected pressureand the set point can cause the pressure controller to generate anelectric signal to open or close a valve, thereby controlling chamberpressure. Embodiments of the present invention provide a pressure gaugewith integrated pressure control capability. Because pressure gaugesaccording to the teachings of the present invention include integratedpressure control capability, the need for a separate pressure controlleris eliminated.

FIG. 3 illustrates a semiconductor manufacturing system 50 that includesa process chamber 52, a pressure gauge with integrated pressure controlcapability 54 (“pressure gauge 54”), a throttle valve 56, and a valvedrive 58. Valve 56 can be a throttling gate valve, a poppet valve, abutterfly valve or any other valve known in the art. In system 50,process chamber 52 can receive a flow of fluid (e.g., gas flow 60),typically, from a mass flow controller (not shown). The fluidconstituting gas flow 60 can depend on the particular manufacturingprocess being carried out in process chamber 52 and can include gasvapor mixes. Pressure gauge 54 can read the pressure in process chamber52 and compare the sensed pressure with a set point. The set point canbe provided by way of a digital or analog set point signal 62 from acontrol computer which monitors the overall system process or by anotherdevice not shown) or other device. In another embodiment of the presentinvention a set point value can be stored at gauge 54.

If there is a difference between the sensed pressure and the set point,pressure gauge 54 can generate a control signal (e.g., signal 64) andcan communicate the control signal to valve drive 58. As most currentvalve drive systems operate on analog signals, control signal 64 can bein analog form. However, as would be understood by one of ordinary skillin the art, control signal 64 can, in other embodiments of the presentinvention, be a digital signal. Based on control signal 64, valve drive58 can throttle valve 56 to regulate the net speed of gas flow out ofpressure chamber 52 (e.g., output gas flow 66). By regulating the speedof a downstream flow, the pressure in an upstream chamber can becontrolled. Thus, by throttling valve 56, the pressure in processchamber 52 is controlled. The pressure can be maintained in asub-atmospheric (e.g., vacuum) state, at atmospheric pressure or aboveatmospheric pressure.

FIG. 4 is a diagrammatic representation of one embodiment of pressuregauge 54 with integrated pressure control. Pressure gauge 54, accordingto one embodiment of the present invention, can include a sensor portion68 and a control portion 69. Control portion 69, in this embodiment ofthe present invention, can include an analog to digital converter(A-to-D converter) 70, a digital signal processor (DSP) 72 and a memory74 (e.g., RAM, ROM, EEPROM, Flash memory, magnetic storage device orother memory known in the art) accessible by DSP 72. Memory 74 can storesoftware instructions 76 for generating a control signal based on thepressure sensed by sensor portion 68. Gauge 54 can include variousinput/output capabilities. For example, gauge 54 can include a serialinterface to support administrative functions such as updating computerinstructions 76. Additionally, gauge 54 can include network interfacesto communicate with other flow control devices, administrative computersor other device capable of communicating over a network. In oneembodiment of the present invention, sensor portion 68 and controlportion 69 can be integrated in a housing 78. Housing 78 can beconfigured to mount to or in a process chamber (e.g., process chamber 52of FIG. 3) according to any scheme known in the art. Gauge 54 can beconfigured such that sensor portion 68 can be at least partially exposedto the fluid in the process chamber to read the pressure in the processchamber.

Sensor portion 68 can include mechanical and/or electrical componentsassociated with a pressure sensor. As an example, sensor portion 68 caninclude a diaphragm capacitance sensor. Typically, in a diaphragmcapacitance sensor, there is a thin metal or ceramic diaphragm that isexposed on one side to the process gas (e.g., the gas in process chamber52 of FIG. 3). On the other side of the diaphragm, there is typically avacuum. The metal diaphragm is usually on the order of 1/1000-inch thickor less, depending on the characteristics of the particular capacitancediaphragm sensor. As the pressure in process chamber 52 increases, theamount of deflection in the metal diaphragm changes. This can cause thecapacitance between the diaphragm and another metal plate or electrodeto change. A circuit connected to the diaphragm and metal plate canoutput an analog sensor voltage that is influenced by the capacitancebetween the diaphragm and metal plate. Thus, sensor portion 68 canoutput a sensed pressure signal corresponding to the pressure in theprocess chamber. Other example sensors include, but are not limited to,pirani sensors, hot cathode sensors, cold cathode sensors, thermocouplebased sensors or any other pressure sensor known in the art.

According to one embodiment of the present invention, sensor portion 68can output the sensed pressure signal as an analog signal. A-to-Dconverter 70 can convert the analog sensed pressure signal to a digitalpressure signal and forward the digital pressure signal to DSP 72.Additionally, A-to-D converter 70 can receive an analog set point signaland convert the analog set point signal to a digital set point signal.In another embodiment of the present invention, the set point can bereceived as a digital set point signal or can be stored in memory (e.g.,memory 74) as a set point value. DSP 72 can execute instructions 76 tocompare the sensed pressure to the set point and generate a digitalcontrol signal accordingly. A-to-D converter 70 can convert the digitalcontrol signal to an analog control signal and forward the analogcontrol signal to a valve drive (e.g., valve drive 58 of FIG. 3). Inanother embodiment of the present invention, gauge 54 can send a digitalcontrol signal to the valve drive.

Thus, control portion 69 can provide pressure control functions. DSP 72can process software instructions stored in memory 74 to apply variousalgorithms to compare the sensed pressure with a set point. If adifference between the measured pressure and the set point is detectedwhen pressure gauge 54 compares the measured pressure to the set point,the pressure gauge can generate a control signal. A valve drive can beresponsive to the control signal to open or close an associated valve,thereby regulating pressure in the process chamber.

Control portion 69 can also implement self-diagnostics. For, example, ifsensor portion 68 is a diaphragm capacitance sensor, DSP 72 can executesoftware instructions 76 to determine if the capacitance or sensedpressure exceeds or goes outside of predetermined bounds (e.g. goesoutside performance parameters) and, if so, generate an alarm.Additionally, DSP 72 can monitor the temperature in the sensor and ifthe temperature goes out of predefined bounds, can trigger an alarm. Inthis case, the alarm can be generated at gauge 54 rather than at aseparate tool.

It should be noted that the embodiment of FIG. 4 is provided by way ofexample only and the sensor portion and control portions of the gaugecan comprise various components for sensing a pressure and generating acontrol signal in response to the sensed pressure. The control portionand sensor portion can include shared and/or separate components. Thesensed pressure can be communicated from the sensor portion to thecontrol portion as an analog signal, a digital signal or in any othermanner known in the art.

FIG. 5 is a flow chart illustrating one embodiment of a method forpressure control according to the present invention. At step 100, agauge with integrated pressure control (e.g., pressure gauge 54 of FIG.3 and FIG. 4) can measure a pressure. The pressure can be assessed usingany pressure measurements scheme known in the art. The gauge withintegrated pressure control, at step 102, can compare the sensedpressure to set point 104. If there is a difference between the sensedpressure and the set point, as determined at step 106, the gauge cangenerate an error signal. At step 108, the gauge with integratedpressure control can generate a control signal based on the differencebetween the sensed pressure and the set point.

In one embodiment of the present invention, the gauge can generate thecontrol signal by executing a computer program that can include acontrol algorithm, stored as a set of computer instructions on acomputer readable memory (e.g., EEPROM, RAM, ROM, flash memory, magneticstorage, optical storage or other computer readable memory known in theart). The control algorithm can calculate the digital control signalusing any control scheme known in the art, including, but not limited toa proportional-integral (“PI”) control scheme, aproportional-integral-derivative (“PID”) control scheme, a modified PIDwith offset or other control algorithm known in the art. The controlsignal can be communicated to a valve drive (step 110) in digital oranalog format. These steps can be continually repeated (step 112) tomonitor and control pressure over time.

The present invention provides advantages over prior art pressuremonitoring and control systems. Because the process chamber is typicallyisolated from vibrations, a gauge with integrated pressure controlcapability will experience significantly less vibration than a valvedrive with pressure control capability and, consequently, willexperience less vibration induced noise. Additionally, a vacuum gaugewith pressure control capability will experience less interference fromthe high voltage DC motor in the valve drive than a pressure controllerlocated at the valve drive because the gauge with integrated pressurecontrol can be located away from the valve drive.

Furthermore, the present invention offers advantages with respect toease of pressure controller replacement and repair in comparison topressure controllers integrated at the valve drive. To replace ormaintain a valve drive, an operator must shut down the semiconductormanufacturing system, evacuate any poisonous or corrosive gases from thesystem, and then access the typically cumbersome and inconvenientlylocated valve drive. Thus, replacing valve drive can require substantialamounts of time. Gauges, on the other hand, are generally removablyattached to the process chamber and are easy to remove and replace,decreasing the amount of downtime required if the pressure controllerexperiences inaccuracy or other difficulties.

While the present invention has been described in terms of integratingpressure control capability primarily with a capacitance diaphragmgauge, the pressure controller can be integrated with other forms ofgauges. While various gauges, including parini gauges, thermocouplegauges, cold cathode gauges, and hot cathode gauges, typically do notinclude significant on-board electronics, pressure control circuitry canbe added in the same physical housing. In gauges such as cold cathodegauges that typically use very high voltages, shielding can be used toseparate pressure control components from the sensor portion whileremaining integrated in the same physical housing. Moreover, while thegauge with integrated pressure control has been described primarily interms of a gauge used to sense and control pressure in a processchamber, embodiments of the present invention are suitable for a varietyof applications requiring pressure sensing and control.

Although the present invention has been described in detail herein withreference to the illustrative embodiments, it should be understood thatthe description is by way of example only and is not to be construed ina limiting sense. It is to be further understood, therefore, thatnumerous changes in the details of the embodiments of this invention andadditional embodiments of this invention will be apparent to, and may bemade by, persons of ordinary skill in the art having reference to thisdescription. It is contemplated that all such changes and additionalembodiments are within the spirit and true scope of this invention asclaimed below.

1. A device for pressure sensing and control comprising: a sensorportion operable to sense a pressure; a control portion operable to:compare the sensed pressure to a set point; generate a control signalbased on a difference between the sensed pressure and the set point; andoutput the control signal; and wherein the sensor portion and controlportion are integrated in a housing.
 2. The device of claim 1, whereinthe sensor portion further comprises a diaphragm capacitance sensor. 3.The device of claim 1, wherein the control portion further comprises: ananalog to digital converter; a digital signal processor; a memoryaccessible by the digital signal processor storing software instructionsexecutable by the digital signal processor.
 4. The device of claim 3,wherein: the sensor portion is operable to output an analog sensedpressure signal; the analog to digital converter is operable to: receivethe analog sensed pressure signal; and convert the analog sensedpressure signal to a digital sensed pressure signal; and wherein thesoftware instructions comprise instructions executable by the digitalsignal processor to: receive the digital sensed pressure signal; comparethe sensed pressure signal to the set point; and generate a digitalvalve control signal.
 5. The device of claim 4, wherein the analog todigital converter is further operable to convert the digital valvecontrol signal to an analog valve control signal.
 6. The device of claim4, wherein the software instructions are further comprise instructionsexecutable to perform self diagnosis.
 7. The device of claim 1, whereinthe housing is configured to be coupled to a process chamber.
 8. Thedevice of claim 6, wherein the sensor portion is configured to bepartially exposed to a process gas in the process chamber when thehousing is coupled to the process chamber.
 9. The device of claim 1,wherein the sensor portion can comprise one of a parini gauge, athermocouple gauge, a cold cathode gauge, or a hot cathode gauge.
 10. Asystem for pressure control comprising: a process chamber; a valve influid communication with the process chamber; a valve drive responsiveto a control signal to open and close the valve; a gauge with integratedpressure control coupled to the process chamber, the gauge withintegrated pressure control comprising: a sensor portion at leastpartially exposed to a fluid in the process chamber operable to sense apressure in the process chamber; a control portion operable to: comparethe sensed pressure to a set point; generate the control signal based ona difference between the sensed pressure and the set point; and outputthe control signal; and wherein the sensor portion and control portionare integrated in a housing.
 11. The system of claim 10, wherein thesensor portion further comprises one of a diaphragm capacitance gauge.12. The system of claim 10, wherein the control portion furthercomprises: an analog to digital converter; a digital signal processor;and a memory accessible by the digital signal processor storing softwareinstructions executable by the digital signal processor.
 13. The systemof claim 12, wherein: the sensor portion is operable to output an analogsensed pressure signal; the analog to digital converter is operable to:receive the analog sensed pressure signal; and convert the analog sensedpressure signal to a digital sensed pressure signal; and the softwareinstructions comprise instructions executable by the digital signalprocessor to: receive the digital sensed pressure signal; compare thesensed pressure signal to the set point; and generate a digital controlsignal.
 14. The system of claim 13, wherein the control portion isfurther operable to communicate the digital control signal to the valvedrive.
 15. The system of claim 13, wherein the analog to digitalconverter is further operable to convert the digital valve controlsignal to an analog valve control signal.
 16. The system of claim 13,wherein the software instructions are further comprise instructionsexecutable to perform self diagnosis of the device.
 17. The system ofclaim 10, wherein the sensor portion can comprise one of a parini gauge,a thermocouple gauges, a cold cathode gauge, or a hot cathode gauge. 18.A gauge with integrated pressure control comprising: a pressure sensorto output a sensed pressure; a processor coupled to the pressure sensor;a memory accessible by the processor storing computer executable by theprocessor, the computer instructions comprising instructions executableto: receive the sensed pressure; compare the sensed pressure to a setpoint; and generate a control signal based on a difference between thesensed pressure and the set point.
 19. The gauge of claim 18, whereinthe computer instructions further comprise instructions executable toperform diagnosis of the gauge.
 20. The gauge of claim 18, wherein thegauge is operable to output the control signal to a valve drive.